multiple definitions of device ids between files are combined

[Ryan Harper]

There was a question as to what behavior we would see if multiple yaml files were included that reference the same device. The 05-snappy.yaml is a catch-all "DHCP on the first physical device called eth0" which generates a [Match]\nOriginalName=eth0. The second config applies a static IP and matches based on mac. The resulting eth0.* networkd files are a combination of both configurations.

I believe this is expected behavior but it does mean that if something like cloud-init generates networking configuration from user-data then it cannot keep existing netplan configurations around.

I'll leave this bug here which may be rejected as Invalid if this is expected behavior; It's likely not a bug since documentation indicates that the device identifiers must be unique

https://git.launchpad.net/netplan/tree/doc/netplan.md#n51

However, if this is the case, it would be reasonable to emit an error when they're not if the property in the documentation holds.

root@ubuntu:/etc/netplan# apt-cache policy nplan
nplan:
  Installed: 0.18
  Candidate: 0.18
  Version table:
 *** 0.18 500
        500 http://archive.ubuntu.com/ubuntu zesty/main amd64 Packages
        100 /var/lib/dpkg/status
root@ubuntu:/etc/netplan# lsb_release -rd
Description: Ubuntu Zesty Zapus (development branch)
Release: 17.04

root@ubuntu:/run/systemd/network# ls -al /etc/netplan/*.yaml
-rw-r--r-- 1 root root 63 Feb 15 18:48 /etc/netplan/05-snappy.yaml
-rw-r--r-- 1 root root 822 Feb 15 18:50 /etc/netplan/52-bridge.yaml

root@ubuntu:/etc/netplan# cat *.yaml
network:
  version: 2
  ethernets:
    eth0:
      dhcp4: true
network:
    ethernets:
        eth0:
            addresses:
            - 10.11.12.13/24
            match:
                macaddress: '52:54:00:12:34:00'
            set-name: foobar0
        eth1:
            match:
                macaddress: '52:54:00:12:34:02'
            set-name: eth1
        eth2:
            match:
                macaddress: '52:54:00:12:34:04'
            set-name: eth2
    bridges:
        br0:
            addresses:
            - 192.168.14.2/24
            interfaces:
            - eth1
            - eth2
            parameters:
                ageing-time: 250
                priority: 22
                forward-delay: 1
                hello-time: 1
                max-age: 10
                path-cost:
                    eth1: 50
                    eth2: 75
    version: 2

root@ubuntu:/etc/netplan# netplan generate
root@ubuntu:/etc/netplan# cd /run/systemd/network/
root@ubuntu:/run/systemd/network# ls -al
total 32
drwxr-xr-x 2 root root 200 Feb 15 18:51 .
drwxr-xr-x 19 root root 460 Feb 15 15:39 ..
-rw-r--r-- 1 root root 116 Feb 15 18:51 10-netplan-br0.netdev
-rw-r--r-- 1 root root 52 Feb 15 18:51 10-netplan-br0.network
-rw-r--r-- 1 root root 90 Feb 15 18:51 10-netplan-eth0.link
-rw-r--r-- 1 root root 118 Feb 15 18:51 10-netplan-eth0.network
-rw-r--r-- 1 root root 69 Feb 15 18:51 10-netplan-eth1.link
-rw-r--r-- 1 root root 126 Feb 15 18:51 10-netplan-eth1.network
-rw-r--r-- 1 root root 69 Feb 15 18:51 10-netplan-eth2.link
-rw-r--r-- 1 root root 126 Feb 15 18:51 10-netplan-eth2.network
root@ubuntu:/run/systemd/network# cat *eth0*
[Match]
MACAddress=52:54:00:12:34:00
OriginalName=eth0

[Link]
Name=foobar0
WakeOnLan=off
[Match]
MACAddress=52:54:00:12:34:00
Name=foobar0

[Network]
DHCP=ipv4
Address=10.11.12.13/24

[DHCP]
RouteMetric=100

[Mathieu Trudel-Lapierre (cyphermox)]

This is expected behavior:

       /* Files with asciibetically higher names override/append settings from
         * earlier ones (in all config dirs); files in /run/netplan/
         * shadow files in /etc/netplan/ which shadow files in /lib/netplan/.

You are meant to be able to generate cross-referencing configuration files or global configs which can then be invalidated by later files referencing the same devices and overriding the settings -- this allows shipping "global" configuration files with defaults, which are then customized to a user's liking via later files, possibly in a different directory.

My understanding is that it however means that you will not be able to reuse the name "eth0" as the name of a bond or another type of device if it has already been defined as an ethernet.

[Ryan Harper (raharper)]

Ensuring that netplan parses the while file is not the same as the order in which netplan parses individual configuration files.

If I ship the attached file as the *only* netplan configuration file on the whole system surely I can expect netplan to *parse* the whole file, and then generate a configuration.

I suspect things like bridged vlan bonds is going to have a certain amount of cross referencing that's going to be problematic for single-pass rendering.

[Ryan Harper (raharper)]

Ignore my comment above, I was confused.

For this bug

1. We should document the id namespace issue
2. Netplan should detect and generate a warning/error message so folks don't continue to ship (and are at least pointed to the file further up in the hierarchy that is claiming/defining the id.